Reptile
Skin Basics

Skin
ConstructionReptile skin has some
things in common with mammal skin...and some things that are are not. Iguanas
differ from other reptiles in that their pus, while made of the same things as
mammalian and other reptilian pus, is solid, rather than flowing. Reptile
skin (integument) is comprised of two main layers, the epidermis and the dermis.

Epidermis: characterized
by complete covering of keratin (the same stuff that makes up mammalian hair and
mammalian, avian, and reptilian nails/claws also makes up the plates we call "scales").
The keratin may be thick, as on the belly and tail, or thin, as on the dewlap.
The hard spikes on such lizards as bearded dragons and horned lizards are just
harder bits of integument, as are the keeled ridges on many snakes' scales and
some lizards, such as some iguanas. The keratin is composed of many layers of
very thin, flat cells. The closer they get to the surface of the reptile, the
more highly compacted they are as they are pressed against by new keratin cells
being formed lower down in the epidermal layer, the stratum germinativum. Three
such layers of increasingly compacted keratin cells are formed, called, from the
surface inward toward the stratum germinativum, the Oberhautchen layer, the beta-keratin
layer, and the alpha-keratin. Some reference the epidermis as being three layers:

Stratum corneum: heavily
keratinized outer layer.

Intermediate
zone: composed of stratum germinativum cells in various stages of development.

Stratum germinativum:
the deepest layer, consisting of cuboidal cells. Undergoes mitosis to form the
intermediate zone.

During shedding (ecdysis), the mitosis in the stratum germinativum forms the new
cells moved up to the intermediate zone and those cells up to the stratum corneum.
It is during this time that the skin is metabolically active and it in this period
of activity that healing will occur. Otherwise, skin is essentially inert.

Exception to the norm...
The exception to the above is the chelonians. Their shell, which many people
think is just bone, is actually covered with living tissue composed of keratinized
epidermis covering the underlying dermal plate which is itself the chelonians
vertebrae and rib cage. (Thus, the practice of piercing a chelonians's shell to
put a ring in with which to tether chelonian (which is in itself inhumane), or
to decorate it with stud earrings, is akin to our puncturing our skulls.)

Dermis: consists of connective
tissue. In some reptiles, there may be small bones called osteoderms. These are
what form the distinctive specialized scales on savannah monitors and crocodilians,
for example.

Reptile
skin heals much more slowly than mammalian skin, often taking about 6 weeks for
the defect to be fully restored.

InfectionsReptiles, being
reptiles, do not have hair follicles. Not having hair follicles means they don't
get complications that hair follicles get - like acne (pimples). Since they don't
have these oil-producing follicles nor the bacteria and things which live inside
the follicles, there are no follicles to get plugged with dirt or oil - so, no
"pimples." Lumps and bumps, then, though they may be filled with pus,
are not to be treated like an occasional pimple, but like the potentially dangerous
bacterial or parasitic infection that they really are.

Noted
reptile vet John V. Rossi, in his chapter on Dermatology in Mader's book, Reptile
Medicine and Surgery (pp. 104-117), notes the following skin conditions encountered
in reptiles that may be described by reptile keepers as "lumps", "bumps"
or "scrapes".

Abscess:
most common dermatologic problem seen in reptiles; a variety of gram-negative
bacteria are involved in these infections. Reptiles do not have the enzymes required
to break down these masses, so the mass must be surgically removed (including
the use of sterile instruments in a sterile field) and appropriate antibiotics
administered. Carbuncles, another condition, is one of multiple abscesses connected
by sinuses which may invade deeper into the underlying tissues.

Abrasions: a traumatic
removal of the epidermis, such as when the reptile tries to escape through a too-small
opening in his enclosure, or a turtle scrapes against an inappropriate rock, such
as lava rock. Abrasions from repeated trauma, such as rostral rubbing or snout-banging
may become infected, turning into abscesses.

Blisters/Bullae:
The difference between the two is simply a matter of size. In both cases, they
result from being kept in an environment that is too moist (terrestrial reptiles),
or dirty water (aquatic and semi-aquatic turtles). While they may be free of bacteria
when first formed, when they break, they permit bacteria to enter through the
resulting defect, which can lead to localized infection or septicemia ("blood
poisoning", or system-wide infection).

Crusts:
dried intracellular fluid, blood and other matter that forms on top of a laceration
or abrasion. Before these areas dry and become crusty, they will be seen and felt
as a thin, wet, clear or yellowish fluid.

Cysts:
these large, fluid filled structures are most commonly associated with subcutaneous
parasites, such as tapeworm. Other causes include the traumatic separation of
the epidermis from the dermis below, burns, or other severe trauma.

Discoloration: when not
associated with stress, breeding season, bruise or shedding, they signal a bacterial
or fungal infection, one that may be affecting just the skin, or may be systemic
in nature. Both require immediate diagnosis and appropriate treatment.

Edema: some localized
swelling may occur at an injection site or after some dewormers.

Nodules: granulomas which
are usually associated with many kinds of infection, from bacteria, fungi or parasites.
In order to appropriately treat the underlying condition, proper diagnosis must
be made.

Parasites:
besides ticks and mites, there are various endoparasites which live part of their
life cycle inside the host, and then migrate outwards, through organs and tissues,
to form small nodes or bumps under the skin, which may or may not create exudates
or crusts. The parasite does cause an irritation, which, when in its usual host,
will cause the host to rub up against something to 'scratch the itch'. This serves
to break open the already inflamed skin, freeing the parasite to move on to its
next stage. With the lack of proper quarantine and generally filthy conditions
endemic in the pet trade, animals - and humans - are coming into contact with,
and playing host to, parasites which don't normally inhabit them. This can result
in a parasitic nodule sitting under the skin, causing an inflammatory reaction.
If not removed properly, it can cause stress, leading to infection...or infect
the human who carelessly picks at it.

Patches
of skin color/texture change: may be associated with fungi or bacterial infections,
necessitating proper diagnosis to determine the required treatment.

The skin is the body's largest organ and plays an important role in keeping the
body healthy. The skin of all vertebrates serves to keep bodily fluids in the
body, and keep bacteria, fungi, and parasitic organisms that don't belong in the
body out of it. When a problem occurs in the skin, it is important that it be
properly evaluated.

Wound healing, while it takes longer in reptiles, is similar to that of mammals:
a mix of proteinaceous fluid and fibrin start to form in the defect, filling it
in and forming a scab. Epithelial cells start to move into the area under the
scab, forming a thin layer. As these cells increase in number, the layer thickens.
While this is going on, macrophages and heterophils, the body's clean-up crew,
move in under the scab layer and clean up bacteria and cellular debris. Since
the most rapid period of growth and repair is during the shed period, which occurs
every 4-6 weeks in a healthy reptile (and may occur more frequently over and immediately
around the site of an abscess or wound), sutures should, if possible, be left
in place for at least 4-6 weeks or until after the next shed, if the reptile starts
a shed within a week or so after the surgical procedure.

Interesting
note... Wounds and incisions that are oriented
cranially-caudally (lined up in the direction from head to tail) heal faster than
transverse (side-to-side) ones.

New reptile owners who try to get answers by email or posts in forums, or even
by posting pictures, are just wasting what may be precious time: they need to
get their reptile to a reptile vet for proper diagnosis, treatment, and learn
what they may need to fix in the reptile's captive environment to ensure that
the condition heals uneventfully and does not occur again.

A
Note On SuturesSome
of the sutures used in stitching up inside the iguana as well as on the skin surface
are "dissolving" stitches. That is, over a period of time, they dissolve
away and fall out. They do not always fall out, even though they may have dissolved
under the epidermis. These stitches should be removed to prevent them getting
caught on anything - or falling out and being ingested by the reptile, child or
pet.

Sutures placed
in the gastrointestinal tract may end up passing through the intestine and cecum,
being excreted with the urates and feces. Or, they may lodge in the tract, kidney
or bladder. If the latter occurs, uric acid stones may form around them. This
can cause impaction or difficulty voiding wastes, or they may lodge high enough
in the cecum or intestine that they require surgery to remove them.

Color (or
why an albino isn't always an albino)Really,
there ought to be truth-in-advertising when it comes to calling any reptile who
is missing most - but not all - of its skin pigments "albino." What
triggered the addition of this section in my reptile skin article is yet another
"albino" iguana for sale, this one for $8,000. Like a lot of breeders
and importers who end up with an unusual color morph, they are quick - but not
accurate - in slapping an 'albino' label on it.

Albinism is the lack of melanin in the skin so the skin is white or pinkish (from
the circulating blood). Since pigments give the eyes their color, albinos have
red eyes (so colored from the blood vessels in the eye). Photos of this $8,000
"albino" and others I've seen clearly show that they are not albinos.
This one is clearly very light green and has light brown eyes. That means he is
has some green (made of yellow and blue chromatophores) and very little melanin
- enough to color the eyes brown and create the darker stripes along the tail.
The few other "albino" iguanas for sale throughout the last several
years were similar to this one or had even less of the blue, making them yellow
and white with blue eyes.

In general, reptiles have two sets of cells that produce color, the melanocytes
and the chromatophores:

Melanocytes are present throughout the basal layers of the epidermis. During the
skin-renewal phase of epidermal growth, the melanocytes send pseudopodia into
the melanin-bearing keratocytes to transfer the melanin to the new cells. In crocodilians,
iguanids and snakes, these melanin-bearing keratocytes are in the ß-layer;
in other reptiles, they occur in both the a- and ß-layer.

The chromatophores are layered upon one another in the outer portion of the dermis.
A layer of xanthophores (yellow pigment cells) erythrophores (reddish-purple pigment
cells) and other fat-soluble pigment cells lay just under the basal membrane of
the epidermal layer. Under the xanthophores are several layers of iridiophores
which produce iridescent colors in the range from blue to gold, as well as white
(guanophores and leucophores).

The presence or absence, and density and distribution when present, of the melanocytes
and chromatophores within each layer will determine the color of the reptile -
not some breeder slapping an "albino" label on it. In some static-colored
species, the stacks of chromatophores are absent.